#include<stdio.h>
int main(void)
{
    int a = 1000;
    int *p = &a;  
    int *p1;//
    printf("Before modify\n");
    printf("The a is %d\n", a);
    printf("The *p is %d\n", *p);
    printf("The a's address is %d\n", &a);
    printf("The p is %d\n", p);    
    *p = 20201004;
    
    printf("After modify\n");
    printf("The a is %d\n", a);
    printf("The *p is %d\n", *p);
    printf("The a's address is %d\n", &a);
    printf("The p is %d\n", p);

    *p1 = 111;
    printf("The *p1 is %d\n", *p1);   
    printf("The p1 is %d\n", p1);   
    return 0;
}